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73 450 SLC, 99 SL500
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Discussion Starter #1
I can't find the source of strong gas odor in my 73 450SLC. Inside the cabin and under the hood. I've replaced the fuel pump/filter assembly and the hoses, and the gas cap, replaced all the fuel hoses around the engine (except the 8 short injector hoses). I've sprayed soapy water on all the hoses and connections, but no bubbles. Thinking that the injectors might not be shutting off, I put a can of injector cleaner in the tank -- with no improvement. Also, no drips on the floor or anywhere else.

I've read all the forum discussions, but I can't find anything that describes how to find the source of the gas smell.

Anyone else with this problem? Suggestions on how to find the source?
 

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1988 560sl
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144 Posts
Take it down to the local "Smog Check" shop. They have a thing that goes in the tailpipe that is very sensitive to unburned hydrocarbons. Have them probe around under the hood with it - that thing will hone in on the source right away.
 

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'79 450SL, '04 CLK200 convertible; former A124, W210, A209.
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2,445 Posts
Just a word of caution, given its a D jet and you can't trace the root cause yet I'd be hesitatnt to actually drive it Dave - I assume the smell is a new development that wasnt there before?
 

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'72 350SL, '85 300D, '98 E320, '19 Subaru Outback (sold '14 GLK250)
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11,087 Posts
If the smell is under the hood, watch very carefully while engine is running. Use a flashlight. It is more that likely the injector hoses.

Do they have clamps top and bottom or swaged one end? If they have been replaced, are they the correct 7.5mm ID hose? Are the clamps proper FI type clamps? Some including myself tried 5/16" FI hose - it leaks! As do gear clamps.
 

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73 450 SLC, 99 SL500
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203 Posts
Discussion Starter #6
I've spent the last year and a half getting it drivable. Finally got it registered, so I took it for a (smelly) test drive to replace the 20-year old tires. Next drive will be a short trip to smog station...
 

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73 450 SLC, 99 SL500
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203 Posts
Discussion Starter #7
If the smell is under the hood, watch very carefully while engine is running. Use a flashlight. It is more that likely the injector hoses.

Do they have clamps top and bottom or swaged one end? If they have been replaced, are they the correct 7.5mm ID hose? Are the clamps proper FI type clamps? Some including myself tried 5/16" FI hose - it leaks! As do gear clamps.
Still has the swaged clamps at the injector ends. When I sprayed soapy water on those hoses with engine running, I was expecting to see bubbles at the leak(s), but no. I've followed all the posts about replacing those hoses, but I really don't want to do it if the problem is elsewhere...
 

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'79 450SL, '04 CLK200 convertible; former A124, W210, A209.
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2,445 Posts
If the injector hoses are original I'd replace them pronto as preventive maintenance, regardless if the leak or not. A gent I met here in the club had a Djet for 12 years, never an issue, until it went up in smoke due to a hose bursting.
 

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'72 350SL, '85 300D, '98 E320, '19 Subaru Outback (sold '14 GLK250)
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11,087 Posts
Still has the swaged clamps at the injector ends. When I sprayed soapy water on those hoses with engine running, I was expecting to see bubbles at the leak(s), but no. I've followed all the posts about replacing those hoses, but I really don't want to do it if the problem is elsewhere...
Soapy water is great for air leaks, but not sure it would show a gasoline leak. I would clean the hoses off, maybe spray on some brake cleaner (that would evaporate) . The when they are clean and dry, run engine. You may just see dampness around the swages or clamps. You could try tightening the clamps, but really if these hoses are old, they should be replaced. Many of us have been around this block before.

The hoses are easy enough to change. The FSM has a section on how to cut off those swages and replace with clamps. This post by Droidster (who we haven't seen here for a while!) summarizes what he bought:
Fuel leaks! - 2M 7.5mm ID hose plus enough clamps to replace all those on the fuel system that don't look like the OEM Oeliker ones at bottom of that link.
 

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73 450 SLC, 99 SL500
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203 Posts
Discussion Starter #10
Embarrassing, but I found a cracked (ancient) fuel hose at the regulator. MBGraham is correct, soapy water didn't show bubbles, but the crack subsequently opened up and became VERY visible.
2662680

It turns out that 7.5mm fuel hose isn't stocked by anyone locally, so I had to order a big roll.
 

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Outstanding Contributor
450slc5.0cab 280sl5sp 280se4.5 500se+500slAMG +250seStkW108 350sl4spdX3 500secEuro
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23,012 Posts
I'm also going to be a stocking dealer -- 15 meters! But I need it tomorrow and that's the only way I could get it fast...
15 meters! I just bought 8 because I have so many cars that will need it.
 
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